BUG: Dentry still in use [unmount of 9p 9p]

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 1e5f5a14 ANDROID: x86: Add objtool to MAKE_GOALS
git tree: android12-5.4
console output: https://syzkaller.appspot.com/x/log.txt?x=1767a0f8d00000
kernel config: https://syzkaller.appspot.com/x/.config?x=7dc3dec9bdddbf39
dashboard link: https://syzkaller.appspot.com/bug?extid=6e9fc6ed2622084c544b
compiler: Android (6032204 based on r370808) clang version 10.0.1 (https://android.googlesource.com/toolchain/llvm-project 6e765c10313d15c02ab29977a82938f66742c3a9)

Unfortunately, I don't have any reproducer for this issue yet.

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+6e9fc6...@syzkaller.appspotmail.com

BUG: Dentry 0000000088936ff0{i=0,n=.index} still in use (1) [unmount of 9p 9p]
------------[ cut here ]------------
WARNING: CPU: 1 PID: 383 at fs/dcache.c:1597 umount_check+0x179/0x1c0 fs/dcache.c:1588
Kernel panic - not syncing: panic_on_warn set ...
CPU: 1 PID: 383 Comm: syz-executor.0 Not tainted 5.4.93-syzkaller-00590-g1e5f5a14faba #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x1dd/0x24e lib/dump_stack.c:118
panic+0x285/0x750 kernel/panic.c:221
__warn+0x1fd/0x200 kernel/panic.c:582
report_bug+0x390/0x4d0 lib/bug.c:195
fixup_bug arch/x86/kernel/traps.c:179 [inline]
do_error_trap arch/x86/kernel/traps.c:272 [inline]
do_invalid_op+0x6e/0x110 arch/x86/kernel/traps.c:291
invalid_op+0x1e/0x30 arch/x86/entry/entry_64.S:1029
RIP: 0010:umount_check+0x179/0x1c0 fs/dcache.c:1588
Code: ff 4c 8b 0b 48 81 c5 20 04 00 00 48 c7 c7 63 55 1d 85 4c 89 fe 4c 89 f2 4c 89 f9 45 89 e8 31 c0 55 e8 07 36 b0 ff 48 83 c4 08 <0f> 0b e9 fd fe ff ff 89 e9 80 e1 07 80 c1 03 38 c1 0f 8c d4 fe ff
RSP: 0018:ffff8881b23ffc40 EFLAGS: 00010292
RAX: 000000000000004f RBX: ffffffff8548f7d0 RCX: 44a3382922efb600
RDX: 0000000000000000 RSI: 0000000000000002 RDI: 0000000000000000
RBP: ffff8881e4e7c420 R08: ffffffff814e47a1 R09: ffffed103ee25e08
R10: ffffed103ee25e08 R11: 0000000000000000 R12: dffffc0000000000
R13: 0000000000000001 R14: 0000000000000000 R15: ffff8881efe4b110
d_walk+0x2e9/0x570 fs/dcache.c:1307
do_one_tree fs/dcache.c:1604 [inline]
shrink_dcache_for_umount+0x8a/0x1b0 fs/dcache.c:1620
generic_shutdown_super+0x63/0x2a0 fs/super.c:447
kill_anon_super+0x36/0x60 fs/super.c:1108
v9fs_kill_super+0x48/0x90 fs/9p/vfs_super.c:219
deactivate_locked_super+0xaf/0x100 fs/super.c:335
deactivate_super+0x1b8/0x280 fs/super.c:366
cleanup_mnt+0x432/0x4e0 fs/namespace.c:1102
task_work_run+0x176/0x1a0 kernel/task_work.c:113
tracehook_notify_resume include/linux/tracehook.h:188 [inline]
exit_to_usermode_loop arch/x86/entry/common.c:163 [inline]
prepare_exit_to_usermode+0x2b0/0x310 arch/x86/entry/common.c:194
entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x466f67
Code: ff d0 48 89 c7 b8 3c 00 00 00 0f 05 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48 83 c8 ff c3 66 0f 1f 44 00 00 b8 a6 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffdf4cfea08 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000466f67
RDX: 00007ffdf4cfeadb RSI: 0000000000000002 RDI: 00007ffdf4cfead0
RBP: 00007ffdf4cfead0 R08: 00000000ffffffff R09: 00007ffdf4cfe8a0
R10: 00000000018ce793 R11: 0000000000000246 R12: 00000000004af4e4
R13: 00007ffdf4cffba0 R14: 00000000018ce6f0 R15: 00007ffdf4cffbe0
Kernel Offset: disabled
Rebooting in 86400 seconds..


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[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit: 1e5f5a14 ANDROID: x86: Add objtool to MAKE_GOALS
git tree: android12-5.4

console output: https://syzkaller.appspot.com/x/log.txt?x=15dd591b500000

kernel config: https://syzkaller.appspot.com/x/.config?x=7dc3dec9bdddbf39
dashboard link: https://syzkaller.appspot.com/bug?extid=6e9fc6ed2622084c544b
compiler: Android (6032204 based on r370808) clang version 10.0.1 (https://android.googlesource.com/toolchain/llvm-project 6e765c10313d15c02ab29977a82938f66742c3a9)

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=109c9ebf500000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1400d88cd00000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+6e9fc6...@syzkaller.appspotmail.com

incfs: Can't find or create .index dir in ./file0
BUG: Dentry 0000000050b8e456{i=0,n=.index} still in use (1) [unmount of 9p 9p]
------------[ cut here ]------------
WARNING: CPU: 1 PID: 362 at fs/dcache.c:1597 umount_check+0x179/0x1c0 fs/dcache.c:1588

Kernel panic - not syncing: panic_on_warn set ...

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x1dd/0x24e lib/dump_stack.c:118
panic+0x285/0x750 kernel/panic.c:221
__warn+0x1fd/0x200 kernel/panic.c:582
report_bug+0x390/0x4d0 lib/bug.c:195
fixup_bug arch/x86/kernel/traps.c:179 [inline]
do_error_trap arch/x86/kernel/traps.c:272 [inline]
do_invalid_op+0x6e/0x110 arch/x86/kernel/traps.c:291
invalid_op+0x1e/0x30 arch/x86/entry/entry_64.S:1029
RIP: 0010:umount_check+0x179/0x1c0 fs/dcache.c:1588
Code: ff 4c 8b 0b 48 81 c5 20 04 00 00 48 c7 c7 63 55 1d 85 4c 89 fe 4c 89 f2 4c 89 f9 45 89 e8 31 c0 55 e8 07 36 b0 ff 48 83 c4 08 <0f> 0b e9 fd fe ff ff 89 e9 80 e1 07 80 c1 03 38 c1 0f 8c d4 fe ff

RSP: 0018:ffff8881e865fa20 EFLAGS: 00010292
RAX: 000000000000004f RBX: ffffffff8548f7d0 RCX: 5ff58196cf992900

RDX: 0000000000000000 RSI: 0000000000000002 RDI: 0000000000000000

RBP: ffff8881e946f420 R08: ffffffff814e47a1 R09: ffffed103ee25e08

R10: ffffed103ee25e08 R11: 0000000000000000 R12: dffffc0000000000

R13: 0000000000000001 R14: 0000000000000000 R15: ffff8881eff0dbb0

d_walk+0x2e9/0x570 fs/dcache.c:1307
do_one_tree fs/dcache.c:1604 [inline]
shrink_dcache_for_umount+0x8a/0x1b0 fs/dcache.c:1620
generic_shutdown_super+0x63/0x2a0 fs/super.c:447
kill_anon_super+0x36/0x60 fs/super.c:1108
v9fs_kill_super+0x48/0x90 fs/9p/vfs_super.c:219
deactivate_locked_super+0xaf/0x100 fs/super.c:335
deactivate_super+0x1b8/0x280 fs/super.c:366
cleanup_mnt+0x432/0x4e0 fs/namespace.c:1102
task_work_run+0x176/0x1a0 kernel/task_work.c:113

exit_task_work include/linux/task_work.h:22 [inline]
do_exit+0xcc2/0x2830 kernel/exit.c:812
do_group_exit+0x155/0x2b0 kernel/exit.c:910
__do_sys_exit_group+0x13/0x20 kernel/exit.c:921
__se_sys_exit_group+0x10/0x10 kernel/exit.c:919
__x64_sys_exit_group+0x37/0x40 kernel/exit.c:919
do_syscall_64+0xcb/0x150 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x443829
Code: Bad RIP value.
RSP: 002b:00007ffeab276988 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 00000000004b53b0 RCX: 0000000000443829
RDX: 000000000000003c RSI: 00000000000000e7 RDI: 0000000000000001
RBP: 0000000000000001 R08: ffffffffffffffc4 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000004b53b0
R13: 0000000000000001 R14: 0000000000000000 R15: 0000000000000001

[syzbot]

Auto-closing this bug as obsolete.
No recent activity, existing reproducers are no longer triggering the issue.